The California Department of Education's California Assessment of Student Performance and Progress program has released a set of High School Practice Items in connection to the state-mandated exams to be administered this spring.
As detailed in a previous post, six of the 50 released items relate to high school physics topics. Sixteen are from Life Science, 15 from Earth Science, 9 from chemistry, and 4 from Engineering Design.
Remember: chemistry and physics topics have been combined into the more omnibus "Physical Science" realm of the high school science Performance Expectations (PEs). While NGSS's HS-PS1: Matter and Its Interactions is predominantly chemistry, HS-PS2 Motion and Stability: Forces and Interactions, HS-PS3 Energy, and HS-PS4 Waves and Their Applications in Technologies for Information Transfer are predominantly physics PEs.
Nevertheless, 9 of the 15 released HS-PS items assessed HS-PS1 while 6 were shared among PS2, PS3, and PS4. If there is a blueprint available for the composition of the operational exam, I am not aware of it. So the Practice Items may or may not reflect the mix of the operational exams.
UPDATE: I found the blueprint: for the high school test, see page 8 of the CAST Blueprint. Not surprisingly, it appears the operational exam will include physics items in greater proportion than in the released practice items.
Let's take a look at those six. I will state each item's Item-Level Claim Statement (ILCS). Click the ILCS to see the actual item. My analysis will follow each ILCS.
Identify the relationship between mass and acceleration. [Click to see item.]
In general, the item is perfectly reasonable. It speaks to the interpretation of graphed data obtained through a laboratory activity that might be done in a high school setting. The item links solidly with the corresponding PE (HS-PS2-1: Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration.).
But there is a problem. And I say this as someone who had the privilege of sifting through many, many potential exam items offered by ETS for use in state-mandated testing from 2003 to 2013. The problem is the title of the graph.
Classroom teachers come across as dictatorial joy-crushers when they make any attempt to direct their students to conform to established conventions. Titling a graph is but one such challenge. The title of a scientific graph is Dependent Variable vs. Independent Variable.
The graph on this item is correctly constructed as Acceleration vs. Mass: experimenters would have measured the acceleration of a cart while varying the cart's mass. But the graph is titled Mass vs. Acceleration. I have to assume this was an oversight on the part of ETS and anyone (if there was anyone) tasked with content review.
Mathematically determine the properties of the system using the conservation of momentum of objects in the system.
A fair enough item to assess the corresponding PE (HS-PS2.2: Use mathematical representations to support the claim that the total momentum of a system of objects is conserved when there is no net force on the system.).
Some might object that the mathematics is simplified too much in this item. It does leave open the question of how deep the arithmetic might go in operational items. If you make this question about a neutron and a deuteron combining to form a triton, the principle is same, but the numbers are more formidable.
In the event that anyone tries to champion the new assessments as ground-breakingly novel, consider this released test question from the old Academic Content Standards era: Conservation of Momentum RTQ. In fairness, the new one does have color. And kilograms, rather than tons!
But this brings up an ongoing problem suffered by standards exam item-writers. Standards (now PEs) are often important-sounding principles that turn out to be difficult to write a variety of items for.
Select the design solution that best meets the provided criteria about momentum and force during a collision.
This item reveals the challenges associated with writing questions for PEs like HS-PS2-3: Apply scientific and engineering ideas to design, evaluate, and refine a device that minimizes the force on a macroscopic object during a collision. The item has a very long stem leading to the answer choices. And the choices are quite word-heavy, too.
Students with a firm grasp of the fact that increasing impact time reduces impact force will find their way to the correct answer. The item will make them work for it, though. I'm not faulting anyone here: awkwardness is in the nature of writing items aligned to standards (PEs) like this.
Create a correct mathematical representation to determine the components of gravitational potential energy in the Earth-ball system and kinetic energy.
This one requires a written response and is graded with a rubric.
It is linked to HS-PS3-1: Create a computational model to calculate the change in the energy of one component in a system when the change in energy of the other component(s) and energy flows in and out of the system are known.
Might it connect more directly to HS-PS3-2: Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motions of particles (objects) and energy associated with the relative position of particles (objects)? The clarifications on PS3-2 say "Examples of phenomena ... could include the conversion of kinetic energy to ... energy stored due to position of an object above the earth. Examples of models could include diagrams, drawings, descriptions, ...]
Aligning items to PEs is sometimes a dark art; I'm inclined to grant CAASPP latitude on this matter.
I have reason to suspect Rhett Allain will not approve of dropping a tennis ball from the top of a building and stating that air resistance is negligible. Neglecting air resistance is a simplifying step. Dropping a tennis ball might be a requirement of item-writing guidelines that prohibit scenarios that might cause significant injury. Dropping a cannon ball would inherently render air resistance more negligible, but would also present a greater potential (!) for damage if carried out in real life.
There's some contrivance at work here: Determining the kinetic energy of a dropped ball in reality would involve measuring its mass and its speed. The speed, alone, allows one to determine the height from which the ball was dropped. But the standard demands items, so here we are.
Describe how wavelength is related to the change in the medium.
The PE being addressed here is HS-PS4-1: Use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling in various media. The Disciplinary Core Idea expands this to: The wavelength and frequency of a wave are related to one another by the speed of travel of the wave, which depends on the type of wave and the medium through which it is passing.
One word that doesn't appear anywhere in the HS-PS PEs is "refraction". So we have a judgment call here. Do we assess attainment of this PE by asking about what does or doesn't change at an optical boundary during the process of refraction?
Students must also know what index of refraction refers to and that greater values indicate slower transmission speed in transparent materials. I'm delighted to teach the material; no one gets through my course not knowing how rainbows work. But I might have omitted index of refraction thinking no harm would come to my students based on a strict reading of the PEs and DCIs. I would have been wrong.
There are certainly topics I am skipping based on my reading of NGSS. Which ones will show up in the assessments? Time will tell. I'm not a huge fan of surprises like this.
Minor point: Numerical values were used for the indices of refraction and for the wavelength of the laser. I'm not sure why an infrared wavelength was chosen. When I use lasers in class, I prefer to stick to visible light varieties.
Quantify the change in energy associated with the appropriate change in the relative orientation of the two objects.
The item is a pretty spot-on assessment of the PE here, HS-PS3-5: Develop and use a model of two objects interacting through electric or magnetic fields to illustrate the forces between objects and the changes in energy of the objects due to the interaction.
I like this one because it shows a weakness in my own instruction that will require a bit of patching up.
During classroom instruction, students should be able to examine a number of systems and understand how potential energy changes within them. A rock and the Earth, two opposite charges, two like charges, magnets, springs... Students should know where potential energy is zero and where it is maximized in a given system.
I'll need to work on more explicit instruction of that beyond gravitational systems.
If you made it all the way to the end, pat yourself on the back. This was a long one. I will nourish a hope that we get more released items each year. I was unambiguous about this priority when I served on California's Assessment Review Panel. But panelist's wishes were not always accommodated. I really am trying to be subtle here! In any case, I will try to maintain cautious optimism.
Having said that, I will add that the most fun I had practicing and honing the craft of teaching physics occurred in the years when my students were not assessed with end-of-course exams intended to enforce a measure of accountability. My students in that era did not leave my course with woeful gaps in their physics knowledge. But that's just me shaking my fist at the sky.
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